The 24-year-old he did not believe it when Roy Hodgson called him to break the news, while the head coach himself revealed that he tracked the winger as a club manager
The 24-year-old has represented the Three Lions at all youth levels but will now make the step up to the main side for the first time after playing a key role in the Saints' back-to-back promotions to the Premier League.
The playmaker has taken on extra responsibility at club level, having been handed the captaincy by Nigel Adkins, while he has made an impression against both Manchester City and United so far this term.
"I'm totally shocked, to be honest, and I didn't think the gaffer was being serious when he called to tell me this morning," he told Saints' official website.
|3/1||Adam Lallana is 3/1 with Bet365 to score anytime in England v Ukraine
"It's such a proud accomplishment to be called up to play for your country at any level, but to be called into the senior side is probably the proudest moment of my career so far.
"To play for the Under-21s was a great achievement but this tops it because it is every player's dream to represent your country at the top level."
Lallana's call-up comes after his former Saints team-mate Theo Walcott pulled out of the squad on Monday after suffering from illness, with Daniel Sturridge's fitness is also being monitored.
"I'm looking forward to the experience," he continued.
"I've been called up quite late so I'm realistic in accepting I might not be that heavily involved, but the fact that I will be around such experienced international players is something I am really excited about.
"Even if I don't get the chance to feature, it's nice to know that you are in the thoughts of the national manager.
"I have great memories of my last appearance at Wembley in the Johnstone's Paint Trophy final [where he scored in a 4-1 win over Carlisle in March 2010] so I hope tomorrow will give me even more."
|"I'm realistic in accepting I might not be heavily involved but the fact that I will be around is something I am excited about"
- Adam Lallana
The midfielder, who joined Southampton aged 12, becomes another product of their youth academy to go on to represent their country, with Alex Oxlade-Chamberlain and Walcott well on the way to establishing themselves in Hodgson's plans, and Gareth Bale doing the same for Wales.
The newly promoted team's skipper hailed his club for their development of youth players, pointing out that he does not expect to be the last England graduate from the Saints' production line.
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"We have a lot of talented young English players here and I'm sure that I won't be the last person to represent our country as some of the young lads can go all the way."
England manager Roy Hodgson revealed that the attacker has been on his radar for some time, indicating that he was a potential transfer target when the 65-year-old was a domestic manager in the English top flight.
The Three Lions boss told reporters: "Lallana is a player that I've know about and watched even when Southampton were in [League One] because as a club coach he's been on a radar of players to watch and possibly attempt to buy.
"So I've know about him for some while but it's good that he is confirmed what we've always thought that he is a talent."